Colorectal cancer is the second leading cause of cancer mortality in the United States. This mortality can be reduced by effective screening with fecal occult blood testing, flexible sigmoidoscopy, or colonoscopy, but many adults age 50 and older are not receiving adequate screening. To substantially improve rates of colorectal cancer screening in the United States, new systems to promote screening will need to be implemented and evaluated within health-care delivery organizations to support screening awareness and action by both health-care providers and patients. This study will implement and evaluate interventions to improve systems for colorectal cancer screening in Harvard Vanguard Medical Associates, a large multi-specialty group practice serving approximately 62,000 adults age 50 to 80 at 14 centers in eastern Massachusetts. With a randomized controlled design, the study has four specific aims: 1) To use computerized clinical information systems to identify patients due for screening and to calculate baseline rates of colorectal cancer screening by patient characteristics and by primary care physician and practice group; 2) To assess whether rates of colorectal cancer screening can be substantially increased among adults in primary care by providing patient-specific electronic reminders to primary care physicians during office visits and mailing reminders and cards for fecal occult blood testing to patients; 3) To determine whether the impact of these interventions is influenced by concurrent efforts of health insurance plans to promote colorectal cancer screening; and 4) To evaluate patients' willingness to use a validated web-based tool to estimate their personal risk of colorectal cancer and the feasibility of incorporating this information into colorectal screening practices. This study has important implications for efforts to promote colorectal cancer screening. By evaluating the use of electronic clinical data, electronic reminders for physicians, and mailed reminders and web-based personal risk information for patients, this study has the potential to demonstrate how health-care organizations can use these innovative approaches to maximize rates of colorectal cancer screening among adults that they serve.